Speaker Cable advice request

Greetings
My system comprises Synchrony Two floorstanders and a Simaudio I3RS amp (its a more refined version of the original I-3). The speakers impedance I think dips to around 2.5ohms in the bass and lower midrange.
I am currently using 14AWG thickness silver plated cables, that are known for being slightly energetic in the high frequencies. They are very detailed but lack bass weight and presence/richness on male vocals.
I am looking for something that is more tonally neutral, but also has more body in the lower midrange and bass to compensate for the low impedance. I have tried an old thick cheapo cable I had (probably 10AWG), but I lost a lot of detail with it, although it did solve the richness problems in the lower mids and the bass and made it much more tonally neutral. But the loss of detail made it unlistenable. So what I think I need is a tonally neutral cable with about 9AWG or 10AWG thickness at least in a single run.
 My budget is maximum US$500 a pair for 8-10 foot
I don't have access to some small name cables but what I am considering is the following from the Editors Choice Awards:
(1) Kimber 8TC, which is biwirable into an 11AWG and 13AWG, or single wired 9AWG
(2) PNF Symphony, 12 and 12, or single 9AWG
(3) Nordost Super Flatline (I think Blue Heaven may be a bit lean for my system)
(4) Anything from Audioquest
Robert Harley is his book suggests it is only worth biwring if the cables are separated along the entire length, I think the PNF would give this benefit as each cord has 4 cables in it, but probably not the Kimber 8TC, unless I bought say two 4TC's and combined them as a shotgun.
Any experience or recommendations would be appreciated as where I live its extremely hard to organise demos on my system.
Thanks